Cumulative effect of airfoil-shaped vortex generators and blade aspect ratio on the aerodynamics of wind turbine blades

Wind tunnel experiments are conducted on 3D rectangular blades of s809 airfoil section with four different aspect ratios AR = 1.2, 2.4, 3.6, 4.78, at four different Reynolds numbers Re = 0.75 × 10 5 , 1.0 × 10 5 , 1.25 × 10 5 , 1.5 × 10 5 , over angles of attack, 0 &lt; α &lt; 20°. Both clean blades and blades with Clark-Y airfoil-shaped vortex generators (CAVGs) are tested to measure their 3D aerodynamic characteristics. The combined effects of aspect ratio, Reynolds number, and angle of attack on blades with CAVGs are studied, focusing on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>C</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">max</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> and α stall . Results show that CAVGs delay baseline blades’ stall, enhance C L and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>C</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">max</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> characteristics without significant drag penalty and without loss in aerodynamic stability. It is also observed that a medium- AR blade with CAVGs achieves aerodynamic performance comparable to a clean blade of higher aspect ratio.